Fume hood



Jan. 12, 1932. H SHELDON 1,840,371

FUME HOOD Filed Feb. 8, 1928 2 Sheets-Sheet l Jan. 12, 1932. E, LD N 1,840,371

FUME HOOD Filed Feb. 8, 1928 2 Sheets-Sheet 2 I IIIIlIIIIIIl/l IIIIIIIIIIIIIII I Patented Jan. 12, 1932 EDGAR H. SHELDON, OF MUSKEGON, MICHIGAN FUME HOOD Application filed February 8, 1928. Serial No. 252,911.

My invention relates to fume hoods, and particularly such as are used upon or in connection with chemistry tables in chemical laboratories of schools and colleges.

One of the objects of the invention is to provide a simple, practical and advantageous Jplonstruction of fume hood of the class speci- 'Another object of the invention is to arrange for the advantageous collection and withdrawal of the fumes.

Another object of the invention is to permit the desired disposal of the fumes and to do this without interfering with work on the top of the table on which the fume hood is mounted.

Another object of the invention is to provide a construction which may be called a knock-down construction, that is, a construction which is built and shipped in parts and then readily assembled at the point of use.

' In the accompanying drawings:

Fig. 1 is a front elevation, partly in section, of a fume hood construction embodying my invention;

Fig. 2 is a vertical section of the same taken on line 2, 2 in Fig. 1; I

Fig.3 is a plan view of the same with a portion of the top broken away;

Fig. 4 is a cross section taken on line 44 in-Fig. 1; and

Fig. 5 is a view of a detail of construction.

Referring to the drawings, I show a fume hood device or construction involving an upright pedestal 1 and a substantially horizontal top 2 mounted thereon. The pedestal 1 is adapted to be placed and secured in position on a table top3, or other suitable structure.

The pedestal 1 is preferably made with a substantially uniform lower body portion 1 and a flaring upper portion 1*. This pedestal 1 is preferably made hollow throughout its length, as shown in Fig. 2, whereby it may be used as a conduit or passage for escaping fumes. The lower portion of the pedestal 1 is preferably provided with a damper or'valve 4 which may be conveniently pivoted at 5 and provided with a handle 6 by which it may be manually operated. This I is for the purpose of permitting the passage of heavy fumes accumulating near the top of the table into the interior of the pedestal l for withdrawing same. Clips 7, 7 are pref erably provided and secured to the pedestal 1 to act as stops to prevent an outward swinging movement on the part of the valve or damper 4. Thumb screw 4* holds damper 4 in adjustedposition.

The top 2 is preferably made in a substantially quadrangular form with rounded corners', as shown in Fig. 3. This shape is desirable as it is well adapted to cover the portion of the laboratory table on which the work producing the fumes is being handled; but other shapes or forms could be adopted without departing from the invention.

This top 2 is also preferably hollow throughout, as shown in Fig. 2. It is provided with a fume inlet slot or passage 8 preferably extending substantially around its outer downward edge or margin, with the exception of the portion of the device mounted on the top of the pedestal 1, whereby fumes arising from the table may be directed outwardly in any direction toward the outer edge of the top 2 and will be drawn into the top 2 through the marginal passage or duct 8 no matter in which way or direction they are moving. Thus these fumes will all be collected and none will escape at the sides or ends of the structure, because the duct 8 extends entirely around the structure except at the point of connection with the pedestal 1, at which point the fumes cannot escape laterally because the pedestal is in the way.

As a preferred arrangement the pedestal 1 and top 2 are made as separable parts or members, thereby securing simplicity of construction as well as a knock-down arrangement permitting these parts to be shipped separately and then erected and connected together at the point of use. Both pedestal and top 2 being of substantially flat construction, they can readily be shipped by laying one on top of the other, making a relatively small package, much smaller than if the whole device were shipped in its erected conproper locations and spaced dition with the top 2 projecting laterally from the top of the pedestal. 1, as shown in Fig. 2'

As a simple and practical arrangement for detachably mounting or connecting these parts 1 and 2, the top of pedestal 1 is made open and the top 2 lSzPI'OVlCl-Qd with a clownwardly extending rib or flange 10, the front and side portions of which fit within the top of the pedestal 1, astshown n Figs. 1 and 2,

per portion or part 12 is provided with a downwardly extending overhang or flange 13 and this fits above a lower part or section 14 with space between'these parts capable ot-forming the fume inlet'duct orpassage 8.

" These parts 12 and 14 may be deta'chably secured together by screws 15, the upper part 12 being preferably provided with downwardly' extending lugs 16' andthe lower part 14 being preferably provided with coopera-ting upstanding lugs 17 and the screws 15 being preferably passed downwardly through top portion l2'into and through lugs 16- and into lower lugs 17. A suitable number of screws- 15 with spacing supporting lugs 16' and 17 may be provided, that being shown as indicated Fig. 8; permits the top Q'tobe readily and advantageously construct "ed in a simple, expeditious and inexpensive manner;

' I also show'as a matter of further and specific improvement a number of supporting or holding members for supporting and holding various vessels or other articles-in position to be worked upon or heated by a person using the table. VVh-ile these members could vary in number and-take various forms in accordance with the invention, I preferably employ two vertically extending rods 19,19

and detachably attach them to the top 2' at from other parts sufficiently to give the desired results, As a preferred arrangement these rods 19 have their upper ends screw threaded as at 20 and these threaded ends are adapted to fit into correspondingly threadedsockets in the lower portions of the two front spacing lugs 17, as

SiiQW'Il in Figs. 1, 2 and 3'. Thus the rods 19 maybescrewed mor out of posltlon and used more or less as desired, and furtherarelaid' flat side by side.

' m'cre 'they provide features of the "lmock 'dewn construction, being capable of complete detachment from the top 2 and therefore capable of'bein'g laid lengthwise beside the top 2 and pedestal I when these parts The rods 19 are shown extending down nearly to the table 3 but their length can be varied as desired.

A vessel holding ring 22 is shown secured to one of these rods 19, the ring being fastened to the rod and adjustable along same by a screw thumb piece 23.

A gas burner may be put below a dish or vessel supported by this ring bracket QQ and ae contents heated as done in apparatus of this kind.

In the use of this apparatus heavy iumes will descend, as shown at the leftha-nd side oi Fig. 1 and will enter the lower portion of the hollow pedestal 1 through the aperture or opening'controlled by damper 4. These tum-es will descend through the opening 3* in the table 3' and will be drawn 0% by suitable: suction apparatus.

The lighter fumes will rise, as shown at the righthand side of Fi Land will spread around underneath thetop 2 and into the fume inlet 8. From the latter they will pass into the hollow top 2, and through the latter to the upper diverging end of pedestal 1 and thence" down through the latter whence they will be drawn downwardly by suctioniappa ratus with the heavy fumes'previously referred to. y a i It will be seen that the fumeswi'll be effectively gathered in' this way and will not spread out into the room. The marginal inlet 8 will elfectively collect the fumes no matter in which way'they' move or diverge underneath the top tube. Wherever they travel they will be. finally collected effectively' by the inlet 8 andconveyed'into the hollow top and thence downwardly and out. It will also be seen that ample room is provided underneath the top 2, for effective work and manipulation ot-vessels, burners, and so on, without interfering at all with the hands'or arms of the operator. Alsothat a simple and advantageous arrangement is provided for supporting the vessels and beakers nployed in the experiments and that these supports may be readily manipulated, either attaching them for service or detaching them to get them: out or" the way if not desired. It will also be seen that the handling andcollectionof the fumes, particularly the light ones which arise, i especially advantageous because the fume inlet Sisin a very low position, being as close to the table and work as is practicableand therefore the effect of the suction or operating in this inlet 8 is as great as possible, since it is found experiments that the lower this fume inlet is and the closer to the table and work, the greater is the suction effect onzthe fumes, that effect increasing in much greater ratio than the decrease in distance of the fume inlet from the work and table. In fact, it is found that the effectiveness of the suction: on the fumes varies about in the ratio of the square of the distance of the fume inlet from the work and table. It will also be seen that the substantially fiat undersurface of the top 2 formed by the member 14 greatly facilitates the lateral travel of the fumes and thereby hastens their movement to the fume inlet 8 and so speeds their collection and removal. Also, that the curved or rounded edge 14 of the plate 14 facilitates travel of the fumes into opening or inlet 8 and so permits escape of the fumes at high velocity and so increases efiiciency. Furthermore, the fact that the inlet 8 practically surrounds the fume producing body or device, gives a decided advantage because of the fact that regardless of the direction which the fumes take as they arise, they are bound to come reasonably near the air curtain which develops as a result of the action of the rim inlet. Furthermore, this air curtain is placed in such a position that it does not disturb the flame of the Bunsen burner or other heating device and the cooling eifect on the heating device and work and air currents is reduced to a minimum.

Furthermore the effectiveness of the device is secured with the removal of a minimum quantity of air from the room. This is extremely important, as the ventilation in a laboratory requiring in some instances a hundred or more fume hoods becomes seriously affected and is thrownv out of balance when too great a volume of air is used. For example, these devices re uire for the average laboratory practice a out one hundred twenty-five cubic feet of air per minute for the type of hood illustrated herein. This will gradually take care of any character of fumes that may be created in ordinary laboratory practice and will do so without throwing the ventilation and heating of the laboratory out of balance. Without some such bafile arrangement as herein set forth, or if the fume inlets were arranged in a substantially different manner, as for example 7 either at the side or at the to the volume of air for effective fume col ection would have to be materially increased, thereby involving expense, ventilation disturbance and cross currents in and around the experimental work being done.

It will also be seen that the apparatus is structurally very simple, convenient and advantageous and contains the desirable knock-down features.

It will be understood that changes and modifications may be made without departing from the spirit of the invention.

What I claim is i 1. A device of the class specified comprising an upwardly extending hollow pedestal and a horizontally extending top attached to the upper end of the pedestal extending from one side only and having its interior in communication with the interior of the pedestal, said top having a substantially horizontal flat bottom surface and also having a narrow marginal fume inlet extending around the outer edge of said surface.

2. A device of the class specified comprising an upwardly extending hollow pedestal and a horizontally extending top attached to the upper end of the pedestal and having its interior in communication with the interior of the pedestal, said top having a substantially horizontal flat bottom surface and also having a marginal fume inlet extending around the outer edge of said surface, the top beingiformed by substantially horizontal flat mem ers spaced apart by interior spacing means, and the fume inlet being formed by space between the outer edges of said upper and lower members.

In witness whereof, I hereunto subscribe my name this 7th day of January, A. D. 1928.

EDGAR H. SHELDON. 

